Justin Bieber has a bad cold.
Given that one A-list pop star had already pulled a massive London gig this weekend on health grounds, the bosses must have been worried on behalf of the waiting 50,000 Beliebers in Hyde Park on Sunday evening.
But fortunately the singer opted not to call in sick - and took to the stage for a stonking show as part of the British Summer Time festival (BST) in London.
Here's a round-up of the show.
1. He turned up on time
Bieber got the night off to a heck of a start by doing something truly unheard of among pop stars... he took to the stage at the time he was supposed to.
Justin has been known to keep fans waiting for up to two hours beyond his scheduled stage time in the past.
But not on Sunday night. He appeared at 8pm on the dot - launching straight into Mark My Words and Where Are U Now as he kicked off a 90-minute set.
His punctuality was probably down to the strict curfew times in Hyde Park which means gigs need to be finished by 10pm.
You don't want to upset the neighbours in that area of London, trust us.
2. He was ill
Without being cruel, the audience seemed more into the Justin Bieber concert than Justin Bieber was.
But, to be fair, this was largely because he was feeling unwell.
He told the crowd early on he had a bad cold and said he'd been rubbing some Vicks VapoRub on his nostrils.
"All that medicine stuff is stuck in my nose. I'm having a rough night. Don't judge me," he said.
The audience didn't seem bothered though and more than made up for his low energy levels with plenty of singing and dancing of their own.
It's a fair bet that 50,000 people woke up sounding a little croaky on Monday morning.
3. He's at his best with nothing more than a guitar
As he proved during his recent appearance at One Love Manchester, Justin's talents are most evident when the music is stripped back to basics.
And at BST, one of the most enjoyable moments came when Justin's band went for a tea break and he was left with nothing more than his voice and an acoustic guitar.
He sang beautifully stripped-back versions of Love Yourself and his Major Lazer duet Cold Water as the sun began to set.
It was one of those moments that would feel quite magical if we weren't all so British and embarrassed about admitting stuff like that.
To top it off, he finished the acoustic section with an a cappella rendition of U Got It Bad, the 2001 classic by his original mentor Usher.
4. There was no Despacito
Let's be honest, Justin Bieber has so many hits to his name now that no setlist could ever really be that disappointing.
And on Sunday evening he rattled through practically every song you could wish for from his back catalogue - from Baby through to Boyfriend to What Do You Mean?
But there were two glaring omissions. The first was his David Guetta collaboration 2U - which is currently in the top 10.
The other missing song was even more surprising though - the impossibly catchy record-breaking anthem-of-the-summer Despacito.
The audience was so hungry for the track that they stayed put and began chanting the title after the show had finished.
But given Justin's recent admission that he doesn't actually know all the Spanish words he sings in the chorus, it was probably best that we didn't have a repeat of Burrito-gate.
5. The stars came out
Fresh from partying with Justin in London the night before, Brooklyn Beckham was spotted at the BST gig on Sunday evening, along with mum Victoria and brother Cruz.
But it wasn't just the Beckham clan that turned out to support Biebs.
Kevin Spacey, Daisy Lowe, Conor Maynard, Claudia Winkleman, and Saturdays alumni Mollie King and Una Healy were all there too.
But maximum points go to Dua Lipa, who was spotted in the crowd dancing to Bieber's set after she'd barely left the stage herself.
She made an appearance during Martin Garrix's set right before Justin came on, to sing Scared To Be Lonely - her collaboration with the DJ.
6. Encores are not Justin's thing
As the sky went dark, the audience went crazy as the opening bars of Sorry played out and fireworks went off over Hyde Park.
As one of his biggest hits, it was a fitting way to finish the gig.
The crowd clearly didn't think that was the end of the show, as most stayed right where they were in case he returned to the stage.
But as crew members began to de-rig the set, and Michael Jackson's Beat It played out over the sound system (amazing), most got the message and began to leave.
As fans poured out of Hyde Park, a few excitable young Beliebers began singing Despacito on their way to the tube - which quickly turned into a huge rendition with hundreds joining in.
It would be hard to go home in anything other than high spirits after a show like this.